Reasoning GP · Algorithm · 1-page summary
Raised CRP or ESR in adults
For: adults (16 and over) with a raised CRP and/or ESR, face to face or remote, in hours or OOH. Not for: children (use the fever in children algorithm) or ongoing care of confirmed GCA or PMR (use their protocols).
Core rule: CRP and ESR are prompts to reassess the patient, not diagnoses. Physiology, symptoms, examination and trajectory set the urgency. A modest, discordant or normal marker excludes neither sepsis nor GCA.
0Stop — call 999 now — whatever the CRP
- Suspected infection with NEWS2 ≥7, or NEWS2 5–6 with a single parameter scoring 3 or clinical concern (high-risk sepsis) → 999 pre-alert, immediate transfer.
- Shock or altered consciousness → 999
- New neurological deficit, cauda equina or cord compression symptoms → Emergency admission and urgent MRI.
- While waiting: do not delay transfer for bloods. NEWS2 does not override clinical judgement.
1Triage — sepsis or GCA first (NG253, BSR)
| Finding | Action |
|---|---|
| Infection, high risk | NEWS2 ≥7, or 5–6 plus a single 3 or concern → 999 |
| Infection, NEWS2 5–6 | Urgent senior assessment; hospital if uncertain or unsafe at home. |
| Aged 50 or over | New localised headache, scalp tenderness, jaw/tongue claudication, visual, constitutional or PMR symptoms → GCA (block 2) |
| Well, mild, unexplained | Localise (block 3); repeat after a set interval, with reassessment. |
2Screen — one row is enough
- GCA → prednisolone today + Same-day fast-track. Visual loss, amaurosis, diplopia → steroid now + Same-day emergency eye/acute assessment.
- Spinal infection: new back pain + focal tenderness, night pain, fever, bacteraemia, immunosuppression or IV drug use → Same-day hospital + MRI.
- ANCA vasculitis: rapidly progressive renal impairment, active urinary sediment, pulmonary haemorrhage, mononeuritis multiplex, purpura or ENT disease → Same-day renal/rheumatology.
- Possible myeloma + AKI, hypercalcaemia or cord compression; major cytopenia; film suggesting leukaemia → Same-day
- Myeloma (NG12): 60+ with persistent bone (especially back) pain or unexplained fracture → FBC, calcium, ESR/PV, SPEP + free light chains; suggest myeloma → Suspected cancer pathway
- Lymphoma: unexplained nodes or splenomegaly → consider Suspected cancer pathway
3Assess — localise the inflammation
☐ Obs + NEWS2 if unwell; source ☐ Temporal arteries, girdle, spine, nodes, spleen ☐ FBC + film, renal, LFTs, calcium, albumin, urinalysis + ACR/PCR ☐ SPEP + free light chains if myeloma plausible ☐ Targeted autoimmune tests, imaging. Not: routine procalcitonin or blanket autoimmune screens.
4Classify — only if the screen is negative
- Infection — commonest acute cause; CRP does not separate bacterial from viral. Treat the source.
- PMR — aged 50 or over, new bilateral shoulder and/or hip girdle pain, prolonged morning stiffness. Exclude GCA, infection, cancer, RA, hypothyroidism, myopathy, drugs.
- Inflammatory disease — RA, SLE (CRP often normal in flares), IBD (CRP can be normal; faecal calprotectin), vasculitis.
- High ESR, mild CRP — anaemia, renal disease, age, pregnancy, paraprotein/myeloma, SLE.
- Persistent mild CRP (5–20 mg/L) — obesity, smoking, diabetes, NAFLD, gums. Investigate more if older, symptomatic or rising.
- Uncertain — persistent + weight loss or night sweats → site-specific NG12 route. Document the differential.
5Treat today — only these
- Suspected GCA: prednisolone 40–60 mg daily per the local fast-track protocol, without waiting for tests. Visual loss: IV methylprednisolone 0.5–1 g daily up to 3 days, or 60 mg oral if IV not immediately available.
- Infection: antibiotic by clinical assessment, likely source and NEWS2 — not CRP alone.
- PMR (GCA excluded): prednisolone 15 mg daily, individualised taper; steroid monitoring plan and fracture-risk assessment. Doses: NICE/SPC, BNF, local formulary.
6Refer routinely
- Urgent rheumatology: PMR needing confirmation; ANA positive + multisystem; vasculitis without organ threat.
- PMR treatment beyond 2 years, relapsing GCA or steroid toxicity → specialist.
- Use local GCA fast-track and rheumatology/nephrology Advice & Guidance routes.
7Never reassure by
- A modest or normal CRP/ESR in suspected sepsis or GCA.
- Waiting for CRP/ESR, ultrasound or biopsy before prednisolone in GCA.
- A CRP number to give antibiotics, diagnose sepsis or prove source control.
- CRP/ESR on steroids, or CRP and fever on tocilizumab — suppressed.
- An isolated raised ESR as a cancer referral — use the NG12 tests.
- Repeating CRP/ESR without reassessing the patient.
8Safety-net — say it, then document it
999 “Call 999 or go to A&E if you are very unwell with an infection — confused, breathing very fast, blue or blotchy skin, a rash that does not fade, no urine all day — or get new leg weakness, numbness around the bottom, or lose bladder or bowel control.”
Same-day “Any new loss of vision, blurred or double vision — eye casualty or A&E today. New headache, scalp tenderness, jaw pain on chewing, fever or feeling worse, back pain with fever, much less urine, thirst, confusion or vomiting — contact us today.” Book a review without waiting for the recheck for weight loss, night sweats or growing lumps.
✓Safe to leave primary care only if — all five, documented
No block 0–2 feature; NEWS2 recorded if unwell
GCA symptoms asked about if aged 50 or over
Likely cause named, or uncertainty stated
Tests and a reassessment booked, with owner and date
Safety-net given and documented
Summary of the full Reasoning GP raised CRP / ESR algorithm, which holds the interpretation, tapers, monitoring and evidence. Sources: NICE NG253, NG12 (updated April 2026), NG250, NG234, TA518; BSR GCA 2020; EULAR 2023; BSR/BHPR PMR; BSR 2025 AAV; SPS; MHRA. Clinical reference — follow local pathways and check doses: NICE/SPC, BNF.